In a driver's seat, a passenger's seat, etc., air bag devices which inflate an air bag upon collision of cars to protect the persons in the car are installed. Such an air bag device is constituted from an inflator which is a gas-generating device, an air bag which is inflated by inflator gas, a hose for introduction and distribution of inflator gas which introduces gas from an inflator into an air bag (hereinafter, it will be also mentioned as a hose) and an air bag case in which the above ones are stored.
In recent years, there has been an increasing demand for an air bag device for side collision called a curtain air bag with an object of softening a shock in a side collision and mainly with an object of protection of head in addition to front collision of driver's seat and a passenger's seat. Such an air bag for side collision is stored in a center pillar or in a front pillar in a folded state and, upon collision, inflator gas is introduced into an air bag and the air bag is deployed between a door and a person in the car whereby shock to the person from the side is softened.
Since the air bag for side collision is folded and stored in a center pillar or a front pillar as mentioned above, it is important to store the air bag in a compact form occupying the space as little as possible when the interior design of the car is taken into consideration.
With regard to a hose for introduction and distribution of inflator gas, there have been proposals for an air bag device for protection of the head having a reinforcing liner tube in a gas introducing path to each inflating chamber for supplying the gas firstly to an inflating chamber of a downstream side which is far from an inflator (claims etc. of Japanese Patent Laid-Open No. 11/235,965 A) and for an air bag device for protection of the head where gas for inflation is guided to an inflating portion from an inflator and an inner tube is aligned on an inner surface of a gas flowing portion (claims etc. of Japanese Patent Laid-Open No. 2002/029,359 A).
In those proposals however, although there are descriptions that an auxiliary cloth is utilized for prevention of breakage of an air bag cushion itself by a high-pressure gas from an inflator and that flow of the gas is controlled, there is no specific consideration at all for characteristics of a hose (sometimes such a hose is called as “a liner tube” or “an inner tube”). Particularly, there is no consideration at all for a good storing property when a hose for introduction and distribution of inflator gas is stored in an air bag cushion and then folded and stored in a center pillar or a front pillar and for characteristics around the gas distributing holes of a hose being connected to an inflating portion of an air bag.
Incidentally, as mentioned hereinabove, an air bag for side collision is folded and stored in a center pillar or a front pillar and it is important to store the air bag in a compact form occupying the space as little as possible when the interior design of the car is taken into consideration. Therefore, in a hose for introduction and distribution of inflator gas, it is also an important issue to ensure a high folding property.
In addition, in an air bag for side collision, it is necessary to be deployed immediately at the collision and it is further demanded that the time until the deployment is shorter than that of an air bag for the driver's seat and for the passenger's seat. Thus, it is often to use an inflator where a gas output is relatively big and, therefore, gas pressure is apt to become very high in some portions particularly in a hose for introduction and distribution of inflator gas. Thus, there are problems that, for example, a gas distributing hole portion is deformed due to its burst by pressure of the inflator gas whereby inflated shape of an air bag upon deployment becomes non-uniform and that fiber near the gas introducing opening is cut and scattered into the air bag and melted resulting in breakage of the air bag cushion itself.
As a measure for improving the problems caused by a partial pressure increase as such, there is a method where fiber in large denier or highly strong fiber such as aramid fiber is used so that the strength of an air bag is enhanced as a whole. However, when the fiber is made thick, bulk becomes high causing a problem in a storing property and restriction in interior design of a car and that is a problem while a highly strong fiber is expensive and, when it is used, cost becomes high and that is a problem in view of practical use. Further, in passenger cars, it is often to be demanded for making its weight light in view of improvement in fuel consumption but, particularly when thicker fiber is used, an increase in weight of a hose for introduction and distribution of inflator gas is unavoidable and that disturbs the weight reduction of an air bag device and consequently of the car.
Moreover, it is usual that a hose for introduction and distribution of inflator gas is a hose made of a woven fabric, and it has been also conducted that, after a woven fabric is manufactured using a general-purpose weaving machine such as a water jet loom or a rapier loom, it is cut into an appropriate size and one side thereof is sewn by using sewing thread to give a hose-shaped product (FIG. 2). It has been also conducted to manufacture a tubular-shaped woven fabric by weaving using a cylindrical weaving machine which is used for example for the manufacture of a fire hose. When a gas distributing hole which is necessary for introduction of gas from an inflator into an air bag cushion is formed in a hose manufactured as such, a gas distribution hole is formed on a side which is opposite to the sewn side in the case of a sewn hose. In the case of hose manufactured by a cylindrical weaving machine, a gas distributing hole is able to be formed at any place because a uniform characteristic is available in a circumferential direction. They have been commonly carried out.
It has been also commonly carried out that, when a tubular-shaped woven fabric is manufactured by using a needle weaving machine for the manufacture of seat belt, a gas distributing hole is formed on the opposite side of the non-tubular portion (FIG. 2).
In a gas distributing hole formed on a tubular-shaped woven fabric manufactured by the above-mentioned method, there is a disadvantage that strength of the gas distributing hole does not become high enough and, when gas from an inflator is introduced into an inflating portion of an air bag, there are problems that the area around the gas distributing hole is broken, its shape is deformed and an inflated shape of an air bag upon deployment becomes non-uniform and that fiber near the gas introducing opening is cut, scattered into the air bag and melted resulting in a breakage of the air bag cushion itself.
On the other hand, in a woven product by a cylindrical weaving machine, the shape is cylindrical and weft is continuous. Thus, when said hose is inserted into an air bag cushion and folded into flat, the folding area is hard to make into flat due to rigidity of the weft and thickness becomes hardly small whereby there is a problem in a storing property.